The Diaper Cover and Duo Wrap are both diaper covers. They are made from a polyester fabric that is laminated, making them breathable, yet water resistant. They are soft and pliable, and very comfortable for baby! They both sport the Thirsties double gusset to control leaks. You will need to purchase absorbency to use inside. Let me tell you a little about both options: Thirsties Diaper Cover The Diaper Cover is adjustable in the waist. The Diaper Cover is only available with an Aplix (hook and loop) closure option.  You can use a fitted or fastened prefold diaper inside. Thirsties options include the Duo Fab Fitted, or Duo Hemp Prefold. The prefold will need to be fastened with a Snappi or diaper pins inside the Diaper Cover, to keep the diaper next to the skin and to keep the diaper from shifting. This is very important, or you will have leaks! The Diaper Cover is generous in sizing, so it is to loose to hold a diaper in place without fastening. A fitted diaper has fasteners on the diaper. Thirsties Duo Wrap The Duo Wrap is adjustable in the waist and the rise. The Duo Wrap is available in snap or Aplix (hook and loop) closure options. You can use a fitted diaper, prefold diaper, or insert that replaces a diaper inside. Thirsties options include the Stay-Dry Duo Insert, Duo Fab Fitted, or Duo Hemp Prefold. These are a preferred choice for thinner babies. You may use a trifold prefold or insert inside the Duo Wrap as the wrap is a trimmer fit, and able to hold the absorbency in place near baby’s skin.  You can reuse the cover or wrap 3-5 times between washings. This means you will need less covers/wraps on hand, and will only need one cover/wrap for every 3-5 diapers. Please note that our sizing is general, and each baby is shaped differently. Please check your baby’s measurements to determine which size they should be wearing: http://www.thirstiesbaby.com/customer-center/size-chart/